Outputs still shutting down even with using two outputs and a flyback diode when using PWM.
Will explain the setup:
Davies Craig 115 Pump, PMU16.
Been using the Davies Craig controller but want more control so want to be able to run PWM from the PMU directly.
Used two outputs to share the load and used a flyback diode across the pump. This is the diode I used: Vishay 45V 20A, Schottky Diode, 2-Pin TO-220AC VT2045BP-M3/4W (https://uk.rs-online.com/web/p/schottky-diodes-rectifiers/7620178).
Even with the diode after not very long
FrogJam_Motorsport_PWM_Coolant_Pump_Error.adulog (4.2 MB)
the output was shutting down and overheating even though the board temperature was low.
Screen shots of settings and logs attached. Logs attached below too.
So I do not understand what is going wrong. Does anyone have any ideas? Any help would be greatly appreciated, thanks.
FrogJam_Motorsport_PWM_Coolant_Pump_Error.adulog (4.2 MB)
Hi,
The overheat status refers to the actual transistor for that output. Transistors have internal temperature measurement and will shut down if the temperature exceeds the threshold.
The amount of heat a transistor generates depends on the current of the load, its inductance, and the switching frequency. In this case, you can either triple up the outputs or set the frequency even lower.
Otherwise, this might be too much of a load for our outputs to handle PWM.
Ok that’s good to know thank you.
The pump only draws a maximum of 8amps. Is this too much for two 25amp outputs?
It’s not only about the current.
Switching the transistor on and off creates additional heat compared to having it on constantly. This extra heat depends on the current, load inductance, and switching frequency.
For example, using PWM for lights that don’t have much inductance will generate significantly less heat in the transistors compared to large motors. Even with the same maximum current.
Might be different situation, we had turbo Intake air intercooler pump that shuts down if/when the pump runs dry or cavitates. This happens on the Pump itself, but in the PMU it shows the pump no longer drawing current.
The difference from what you’re seeing is that the channel was continuously active on the PMU despite no current being pulled. Once we got the pump properly primed it would turn on and pull current.
